One in three doctors agree that free drug samples influence prescribing, finds a small but representative US survey published in the Journal of Medical Ethics.
But they also think that other doctors are more likely to be influenced by incentives than they are, the data show.
In March 2003, the research team surveyed 397 members of the American College of Obstetricians and Gynecologists about their relationships with the pharmaceutical industry.
The members were part of a collaborative research network, representing each of the 10 districts covered by the College.
Just over half of those surveyed responded (217).
More than 90% of the respondents thought it was ethical to accept free samples of a new drug from a pharmaceutical company rep.
Similarly, just over half thought it was ethical to accept a lucrative consultancy with a company if they were a "high volume" prescriber of one of that company's drugs.
One in three agreed that their decision to prescribe a drug would probably be influenced by accepting the samples.
But respondents felt that other doctors would be significantly more likely to accept the offer of a free lunch, an anatomical model emblazoned with a drug's name, or a consultancy than they would, even if offered without free samples.
And they also felt that these free "gifts" would still influence the other doctors' prescribing decisions more than it would theirs.
Most doctors said they distributed the free drug samples to their patients to help them out financially or for their convenience. Less than two thirds did so because they felt the drug in question was particularly effective.
Almost two thirds of the respondents were aware of professional guidelines on the relationship between industry and the profession.
But only one in three felt that the relationship should be more tightly regulated. Two fifths felt that it should not be restricted further.
"The generally held view that accepting modest incentive items, such as drug samples is appropriate and primarily of benefit to patients needs to be reconsidered, both by doctors and by policy makers," say the authors. Guidelines need to do more to challenge this view, they add.